It's already been done for you.
The NRA Action Pistol game.
Add some barricades, a few more courses of fire and it's very close in many ways to what you are thinking.
You can download their rule book and stage designs from the NRA website, for comparison.
http://compete.nra.org/documents/pdf...n/act-book.pdf
Add a few wrinkles of your own and it would be an entertaining and easy match to setup and run.
Good luck with it, it should be a winning combination.